In personal computers, sound cards for receiving musical input generally have two channels for receiving stereo audio signals. Each of the signals is digitized for processing or storage in the computer. Most or all sound cards can operate at numerous sample rates, and the highest sample rate at which most or all can operate is 44.1 kHz. Many personal computers with sound cards also include MIDI input ports.
With this hardware, computers can be programmed to receive one or two musical signal inputs through these stereo inputs and process these signals to calculate MIDI data which includes timing, frequency, and intensity for each note. However, if one wishes to obtain MIDI data, or equivalent data, from more than two sources at one time, such as from the six strings of a guitar, additional hardware is required. The available hardware includes a separate electrical connection from each of six pickups, one from each string of the guitar, into a specialized processor with six input channels which generates MIDI or equivalent data that can be transmitted to a computer or other electrical musical device through a MIDI port or a serial port. This equipment is expensive and quite limited in its ability to accurately determine the pitch of each note in a short interval of time once the note is struck and to accurately determine correct timing data for each note. What is needed is a simple hardware device which can get the audio signal information into a personal computer so that, by running powerful software, the personal computer can accurately compute correct timing for each note and correct pitch for each note. From these computations, accurate MIDI, or equivalent, data can be computed.